/*
 * ObjectFactory.java July 2006
 *
 * Copyright (C) 2006, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.core;

import wx.xml.simpleframework.xml.strategy.Type;
import wx.xml.simpleframework.xml.strategy.Value;
import wx.xml.simpleframework.xml.stream.InputNode;

/**
 * The <code>ObjectFactory</code> is the most basic factory. This will
 * basically check to see if there is an override type within the XML
 * node provided, if there is then that is instantiated, otherwise the
 * field type is instantiated. Any type created must have a default
 * no argument constructor. If the override type is an abstract class
 * or an interface then this factory throws an exception.
 *
 * @author Niall Gallagher
 */
class ObjectFactory extends PrimitiveFactory {

    /**
     * Constructor for the <code>ObjectFactory</code> class. This is
     * given the field class that this should create object instances
     * of. If the field type is abstract then the XML node must have
     * sufficient information for the <code>Strategy</code> object to
     * resolve the implementation class to be instantiated.
     *
     * @param context the contextual object used by the persister
     * @param type    this is the object type to use for this factory
     */
    public ObjectFactory(Context context, Type type, Class override) {
        super(context, type, override);
    }

    /**
     * This method will instantiate an object of the field type, or if
     * the <code>Strategy</code> object can resolve a class from the
     * XML element then this is used instead. If the resulting type is
     * abstract or an interface then this method throws an exception.
     *
     * @param node this is the node to check for the override
     * @return this returns an instance of the resulting type
     */
    @Override
    public Instance getInstance(InputNode node) throws Exception {
        Value value  = getOverride(node);
        Class expect = getType();

        if (value == null) {
            if (!isInstantiable(expect)) {
                throw new InstantiationException("Cannot instantiate %s for %s", expect, type);
            }
            return context.getInstance(expect);
        }
        return new ObjectInstance(context, value);
    }
}
